1. Field of the Invention
This invention relates to a dental appliance, and particularly relates to an improved temporomandibular joint appliance, specifically a mandibular orthopedic repositioning appliance (MORA).
2. Prior Art
Acrylic resin temporomandibular joint appliances, such as mandibular orthopedic repositioning appliances (MORA), and their method of manufacture are well known in the art, see for example Gelb, Effective Management and Treatment of the Craniomandibular Syndrome, "Clinical Management of Head, Neck and TMJ Pain and Dysfunction", H. Gelb, ed. Phila., W. B. Saunders Co., 1977; and Lader, "TMJ: Clinical and Practice Management", 1981 by Vadare, Inc. Wantagh, N.Y. One of the main advantages of a mandibular orthopedic repositioning appliance, hereinafter MORA, is the ease with which the appliance can be adjusted to the patient. The material from which it is made, usually a self curing acrylic, can be easily reduced with a handpiece or built up with the acrylic as a chairside procedure.
Typically, after a patients symptoms have been satisfactorily reduced, the patient will undergo one of several other treatments to better stabilize the jaw position, e.g. crown and bridge reconstruction, functional orthodontics, overlay partial dentures or a combination of any of these procedures, see Gelb et al, "Clinical Evaluation of Two Hundred Private Practice Patients with TMJ Syndrome", J. Prosthet. Dent. 1983 Feb. 49:237. Unfortunately, these other type treatments may be unacceptable or impractical for some patients due to financial or time constraints. In these cases a solution is for the patient to wear a MORA as it has been constructed. However, the properties of the material, from which the MORA is constructed, e.g. acrylic, which makes it desirable during the treatment and construction stage, become a disadvantage. The MORA when worn by the patient for an extended period of time can chip, distort and wear down causing a subsequent decrease in the vertical dimension of the MORA. This in turn changes the position of the condyles and their fossae which may bring about the reoccurance of some or all of the patients symptoms.
In the past, amalgam stops have been placed in the acrylic at the points or areas of occlusal contact. These amalgam stops may slow the wearing down process, but for a patient who bruxes persistently they are inadequate, for they rapidly wear down and/or come loose. The wearing down of the occlusal surface of a dental appliance is not only common to MORAS but other type dental appliances, e.g. shore auto-repositioning appliance, myocentric appliance, dentures, etc.